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Factors out track seeking.

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This commit is contained in:
Thomas Harte 2018-05-24 18:45:00 -04:00
parent 57ee6d4e41
commit 8f78e5039e
2 changed files with 27 additions and 9 deletions
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27
Storage/Disk/DiskImage/Formats/WOZ.cpp
View File

@ -90,22 +90,31 @@ int WOZ::get_head_count() {
return is_3_5_disk_ ? 2 : 1;
}
std::shared_ptr<Track> WOZ::get_track_at_position(Track::Address address) {
long WOZ::file_offset(Track::Address address) {
// Calculate table position; if this track is defined to be unformatted, return no track.
const int table_position = address.head * (is_3_5_disk_ ? 80 : 160) + (is_3_5_disk_ ? address.position.as_int() : address.position.as_quarter());
if(track_map_[table_position] == 0xff) return nullptr;
if(track_map_[table_position] == 0xff) return NoSuchTrack;
// Seek to the real track.
file_.seek(tracks_offset_ + track_map_[table_position] * 6656, SEEK_SET);
return tracks_offset_ + track_map_[table_position] * 6656;
}
std::shared_ptr<Track> WOZ::get_track_at_position(Track::Address address) {
long offset = file_offset(address);
if(offset == NoSuchTrack) return nullptr;
// Seek to the real track.
PCMSegment track_contents;
track_contents.data = file_.read(6646);
track_contents.data.resize(file_.get16le());
track_contents.number_of_bits = file_.get16le();
{
std::lock_guard<std::mutex> lock_guard(file_.get_file_access_mutex());
file_.seek(offset, SEEK_SET);
const uint16_t splice_point = file_.get16le();
if(splice_point != 0xffff) {
// TODO: expand track from splice_point?
// In WOZ a track is up to 6646 bytes of data, followed by a two-byte record of the
// number of bytes that actually had data in them, then a two-byte count of the number
// of bits that were used. Other information follows but is not intended for emulation.
track_contents.data = file_.read(6646);
track_contents.data.resize(file_.get16le());
track_contents.number_of_bits = file_.get16le();
}
return std::shared_ptr<PCMTrack>(new PCMTrack(track_contents));

9
Storage/Disk/DiskImage/Formats/WOZ.hpp
View File

@ -34,6 +34,15 @@ class WOZ: public DiskImage {
bool is_3_5_disk_ = false;
uint8_t track_map_[160];
long tracks_offset_ = -1;
/*!
Gets the in-file offset of a track.
@returns The offset within the file of the track at @c address or @c NoSuchTrack if
the track does not exit.
*/
long file_offset(Track::Address address);
constexpr static long NoSuchTrack = 0; // This is definitely an offset a track can't lie at.
};
}